Preheat oven to 425°. Place zucchini in a colander over a plate; sprinkle with 1/4 teaspoon salt and toss. Let stand 10 minutes. Rinse and drain well. Squeeze zucchini to remove excess liquid. Pat dry.
In a large bowl, whisk flour, baking powder, and remaining salt. Cut in butter until mixture resembles coarse crumbs. Stir in zucchini, cheeses, tomatoes, and basil. Add milk; stir just until moistened.
Drop by 1/3 cupfuls into a greased 13x9-in. baking pan. Bake 22-26 minutes or until golden brown. Serve warm. Yield: 1 dozen.